1. Field of the Invention
The present invention relates to a multi-antenna apparatus and a mobile device, and more particularly, it relates to a multi-antenna apparatus and a mobile device each comprising a plurality of antenna elements.
2. Description of the Background Art
A multi-antenna apparatus comprising a plurality of antenna elements is known in general, as disclosed in Japanese Patent Laying-Open No. 2007-97167, for example.
The aforementioned Japanese Patent Laying-Open No. 2007-97167 discloses a MIMO array antenna (multi-antenna apparatus) comprising two antenna elements spaced apart a distance of one half of a wavelength λ of the corresponding radio wave from each other and a substantially U-shaped isolation element (passive antenna element) arranged between the two antenna elements for inhibiting a mutual coupling between the two antenna elements. This isolation element has an electrical length of about λ and is partially grounded on a ground surface. The isolation element is arranged at a position separated from each of the two antenna elements by a distance of about λ/4.
In the MIMO array antenna according to the aforementioned Japanese Patent Laying-Open No. 2007-97167, however, the isolation element must be grounded on the ground surface although the mutual coupling between the antenna elements can be inhibited by providing the isolation element (passive antenna element). Therefore, flexibility of wiring pattern design is disadvantageously reduced.